Concerning the polymerization of propylene, the Ziegler-Natta catalysts can be made from or contain a solid catalyst component, constituted by a magnesium dihalide on which are supported a titanium compound and an internal electron donor compound, used in combination with an Al-alkyl compound. When higher crystallinity of the polymer is desired, an external donor can be used to obtain higher isotacticity. One of the largely used classes of internal donors is constituted by the esters of phthalic acid, (such as for example diisobutylphthalate]. The phthalates are used as internal donors in combination with alkylalkoxysilanes as external donor. This catalyst system gives good performances in terms of activity, isotacticity and xylene insolubility.
The use of this catalyst system has raised health concerns with the use of phthalates.
Some of the tested catalysts contain donors structures having contemporaneously amido groups and ester groups. PCT Publication No. WO2006/110234 describes amino acid derivatives including one carbamate group and one free ester function. The catalysts generated by these structures have very low activity and sterospecificity in bulk propylene polymerization (See Table 2 of PCT Publication No. WO2006/110234).